SUMMARY OF THE INVENTION
The object of the present invention is to provide a simple support structure without the use of active means. The support structure operates solely by utilizing elasticity effects, and its load-supporting section maintains its shape, e.g. its straightness, irrespective of the load, although it moves evenly under the influence of the force until the material yields or breaks. In view of the operation, the mere even displacement under the influence of load is a much better alternative than deflection. One reason for this is that displacement is much easier to compensate than deflection.
This type of support is used e.g. as a frame in various press and calender rolls, and to support the lip of a head box in a paper machine and e.g. blades of coating means in coating devices.
Solutions presently in use are based on hydraulic support structures, the drawbacks of which include high price, required complicated adjustment technology, risk of contamination caused by hydraulic oil, and poor reliability and high weight of the complicated apparatus.
The invention is based on the idea that the total elasticity of the load-supporting area or line (of which there may be several in one and the same structure) with respect to the supporting points of the structure is inversely proportional to the distribution of load over the entire area or line. In other words, the distribution of load and the stiffness distribution of the structure with respect to the supporting points of the structure against the loading force are proportional to each other over the entire load-supporting area. The unbending area or line of the support is moved elastically by a certain force to the same extent both in the middle and at the ends as well as therebetween. In practice, this is achieved by providing one or more additional elastic elements between the central top line of the beam and the supporting points Of the beam in such a way that the sum of the elasticity effects and the deflection is constant over the entire straight portion. Elasticity is assumed to be the inverse of stiffness, i.e. EQU stiffness, K=F/.delta.; elasticity, D=1/K=.delta./F
This principle can be realized in several different ways. In a normal case, an elongated beam supported at the ends is strained by a force uniformly distributed from one end to the other. The longitudinal lines of the beam, straight before loading, are bent by the force into a curved shape. According to the invention, the frame is provided with another elastic element, the elasticity effect thereof adding to the deflection of the beam. This elasticity effect increases towards the ends of the frame so that the sum of the elasticity of the frame and the other elasticity effect is constant everywhere along the beam. This can be arranged simply e.g. by using a deformation, such as flattening, of the longitudinally varying cross-section of a support beam, or a twisting of the support structure or its portion under the influence of the load as an additional elasticity effect. It is also possible to use elastic means or supports to provide the additional elasticity effect.
The invention is characterized in that a stiffness distribution calculated on the basis of the sum of the elasticity effects of said elastic elements with respect to the supporting points within the unbending area or on the unbending line is directly proportional to the distribution of load so that the load-carrying points define a line or sequence which remains unchanged in shape when the magnitude of the load changes.
The advantages of the invention include simplicity, low price, light weight, and reliability.